This study will evaluate the importance of the pigmented epithelium to the retina during maturation of the retina in embryonic development. It will utilize a procedure enabling immature retinas to be isolated from embryos and allowed to mature in vitro either in the presence of an enveloping pigmented epithelium or in the absence of this tissue. It will determine with electromicroscopic and electrophysiological methods whether the presence of the pigmented epithelium is mandatory for the maturation of photoreceptors. Using autoradiographic procedures it will determine whether photoreceptors maturing with and without a pigmented epithelium differ in their ability to incorporate labeled rhodospin precursors.